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  • Updated 06.27.2022
  • Released 09.21.1998
  • Expires For CME 06.27.2025

CNS listeriosis



CNS listeriosis is a rare but very important disease, as it has the second highest case fatality rate amongst food borne diseases. Almost one third of all patients die despite adequate therapy, and hardly one third survive unscathed.

Listeria monocytogenes is a very unusual bacillus, dreaded by the food processing industry as this ubiquitous, harmless saprophyte and is able to survive for years, and suddenly in a Jekyll-like manner, transform into a dangerous pathogen targeting infants and elderly, or sick and immunocompromised persons, with a particular affinity for the brain, causing meningitis, meningoencephalitis, or abscesses.

This fascinating bacillus has evolved to survive adverse environments, biding time for years in a dormant form, inhibiting other competitive organisms in soil and the gut. When conditions are right it can awaken, multiply rapidly, and silently invade a host, hiding and spreading from cell to cell within the intracellular space, evading the immune system and antibiotics. It hijacks various host processes and puts them to work for its benefit.

Almost like a science fiction story, it can travel backwards from the gut and oral mucosa inside the vagus and trigeminal nerves directly to the brainstem.

Systemic or invasive listerial infections mainly afflict persons with a predisposing conditions, including pregnancy, glucocorticoid therapy, other immunocompromising conditions, and extremes of age. Yet, one must always keep in mind, the rare variety of Listeria rhombencephalitis, causing a deceptively benign looking acute brainstem disorder in healthy young adults. If missed, infection may progress within a few days to bulbar palsy, respiratory paralysis, and even death.

Similarly, pregnant women need to know they are at high risk and consider that what looks like a simple urinary infection or flu-like illness may lead to the loss of their baby.

Only certain older antibiotics like ampicillin or penicillin, gentamicin, or trimethoprim-sulfamethoxazole work against it, better than meropenem, whereas third generation cephalosporins actually fail.

We can ignore Listeria only at our peril.

Key points

• Listeriosis is a rare disease, but it is important because it has the second highest case-fatality rate amongst food borne diseases.

• Almost one third with CNS infection die, and hardly one third escape without any major disability.

• This gram positive rod is the bane of the food industry in various ways.

• Risky foods include dairy products, fruits and vegetables, meat products, and fish products; it is even in hospital foods.

• Everyone, but more so persons at high risk, need to be educated about food choices and food handling.

• Many get exposed, but infants, elderly, or persons with impaired immunity are at risk for invasion of the bloodstream or the brain.

• Listeria has the unique ability to silently evade various defense mechanisms, cross barriers, and move intracellularly and within axons.

• Rhombencephalitis is a deceptive but extremely dangerous form of listeriosis, often seen in healthy and young persons.

• Pregnant women are very prone to get listeriosis and may present with an innocuous flu-like illness. It is very important to recognize and treat, as otherwise the baby can become seriously ill.

• A high index of suspicion and early treatment are the key to success as even a few hours of delay may lead to death.

• The therapy of choice for CNS listeriosis is ampicillin or benzylpenicillin combined with an aminoglycoside or TMP-SMX, with meropenem plus gentamicin only as the third alternative.

• The duration of therapy in CNS listeriosis should be at least 3 to 4 weeks in immunocompetent and 6 to 8 weeks in immunosuppressed persons.

• Steroids are probably deleterious and should not be used in CNS listeriosis.

Historical note and terminology

Listeria monocytogenes has long been recognized as a veterinary pathogen causing basilar meningitis and stillbirth in sheep and cattle. It was first described as human pathogen in a patient with a mononucleosis-like syndrome in 1929 (85).

Meningitis due to L monocytogenes was described in 1936, but the first authentic isolation came from a World War I soldier in 1918. His meningitis was attributed to a diphtheroid species. However, the original culture was preserved at the Pasteur Institute in Paris and was identified 20 years later as L monocytogenes. This historical note provides an important reminder that L monocytogenes is sometimes confused and dismissed as a diphtheroid contaminant because of morphological, colonial, and biochemical similarities. A 1949 German epidemic of “granulomatosis infantisepticum” led to the discovery that L monocytogenes caused this severe neonatal infection (47). Brainstem encephalitis or rhombencephalitis due to Listeria was first described in 1957 (37). The first foodborne outbreak of listeriosis was attributed to infected vegetables in a Boston Hospital in 1979 (41).

This gram-positive bacterium has been known by many names, including Listerella hepatolytica, Corynebacterium infantisepticum, Corynebacterium parvulum, and Erysipelothrix monocytogenes. In 1940 taxonomists reached a general agreement to call the species Listeria monocytogenes in honor of the father of antisepsis, Lord Lister (100).

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